The crane was pulling up pilings at the Avalon on Stamford Harbor marina, off Southfield Avenue in the city's Waterside section, when it toppled and fell just before 10 a.m.

"The balance of the crane got out of kilter and the crane began to slip off the barge, and the boom landed on a 47-foot powerboat," said Jacqui Brindley, the marina manager. The boat kept the crane from toppling off the barge and into the water.

The crane, which had been in the marina since Monday, was pulling up pilings damaged during Superstorm Sandy in October, Brindley said.

Varina Wakeman, of the Rowayton section of Norwalk, owner of the damaged boat, said she was relieved no one was hurt in the incident. She said insurance should take care of any damage to her boat, Summer Place, which she and her husband purchased four years ago.

"I'm stunned, frankly," Wakeman said while looking at the boom lying on her $120,000 yacht. "It's kind of ironic that we survived Sandy and it is the repair from the hurricane that did the damage."

Another crane arrived on a barge at 11:15 a.m. in hopes of righting the toppled equipment.

Ralph Corvington, the mechanic at the marina, said he was at the office at the time of the accident, but saw the crane as it had difficulty pulling up one piling. The piling then popped out, sending the crane boom in the opposite direction, he said.

"The momentum took the boom over," Corvington said.

But U.S. Coast Guard Petty Officer Patrick Horn said the crane operator told him he was not pulling anything up at the time, but that a momentum shift pulled the crane down.

Horn said virtually no oil spilled in the accident. An oily sheen in the water apparently came from grease on the crane's boom cables.

On Wednesday afternoon, Stamford Marine Unit Sgt. Robert Monck said the crane owner, Concavage Marine Construction Inc., was racing to get the crane boom lifted off Wakeman's boat before high tide, at just before 10 p.m.

By 4:30 p.m. workers had cut large telephone poles and placed them under the toppled crane's tracks as they prepared to use the second crane to take weight off the toppled equipment.

While no one was aboard Summer Place when the crane went over, a man who was on sail next to it said he heard the crane come down.

The man, who would only give his name as Robert, said he was inside his 47-foot sailboat when he heard a man shout "Stop, stop. No, no," and he heard a rumble.

Part of the boom came to rest on his boat's headstay, a supporting line for the mast.

"You can see they have been doing this for a long time," Robert said of the workers. "It is a shame when something like this happens because you can see that they have a lot of concern for what they do."